The computer scientist Victor Allis notes that typical games between experts last about 150 moves, with an average of about 250 choices per move, suggesting a game-tree complexity of 10360. For the number of theoretically possible games, including games impossible to play in practice, Tromp and Farneb?ck give lower and upper bounds of 101048 and 1010171 respectively. The most commonly quoted number for the number of possible games, 10700 is derived from a simple permutation of 361 moves or 361! = 10768. Another common derivation is to assume N intersections and L longest game for N^L total games. For example, 400 moves, as seen in some professional games, would be one out of 361400 or 1 ? 101023 possible games.

The total number of possible games is a function both of the size of the board and the number of moves played. While most games last less than 400 or even 200 moves, many more are possible.

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